I have a 2000 monte carlo with starting issues. I have seen BCM mentioned a few times on this forum. What does it do and where is it located on the car if it needs to be replaced?

 

body control module. it control electrical parts and sensors. it's locate under the dash on the drivers side. i never replace one in my car before but i think you need to reset it with a scan tool after install. it's probably expensive from the dealer but you can find it at the junk yard, ebay or this link below but make sure the bcm is the same year as your car. here's a picture of what it looks like. scroll down to the bottom of the page.

2004 CHEVY MONTE CARLO BODY CONTROL MODULE BCM

 

I had mine replaced this past summer in my 01 monte, my viper alarm and start were back feeding on it and ruined it. It was around 275 for a new one installed at the dealership.